Gender Homophily in Referral Networks: Consequences for the Medicare Physician Pay Gap • Job Talk

Female physicians—now a quarter of active U.S. doctors—still work puzzlingly less than their male counterparts. This paper suggests an explanation: gender homophily in physician referrals (more same-gender referrals). I propose a new homophily measure and model how referral networks form when doctors decide which specialists to refer to. The model highlights that homophily can arise from either gender-biased preferences or physician sorting by gender into markets. I suggest how to separately identify and quantify both mechanisms in directed networks empirically. Analyzing administrative data on more than 100 million Medicare physician referrals from 2008–2012, I find reduced-form evidence for gender homophily in referrals, and estimate it is predominantly due to biased preferences. As most referrals are still made by men, biased referrals lower demand for female specialists. Homophily explains 10% of the average within-specialty workload gap, and further contributes to the absence of women from lucrative specialties that rely on referrals from men. In the healthcare environment, my results imply that increased participation of female physicians facilitates further integration into related specialties. More generally, my findings suggest that homophily contributes to the persistence of occupational inequalities.